This application is based upon and claims the benefit of priority from the prior Japanese Patent Applications No. 11-272327, filed Sep. 27, 1999; and No. 2000-255461, filed Aug. 25, 2000, the entire contents of which are incorporated herein by reference.
This invention relates to a liquid film forming method wherein a liquid is applied onto a substrate to be processed so as to form a liquid film.
In spin coating method, which has been used in lithographic steps, almost all of a liquid dropped onto a substrate is discharged outside the substrate so that a film is formed from the remainder thereof, which is several percent of the liquid. Therefore, most of the dropped liquid is of no use. Since most of the liquid is discharged, an adverse effect is produced on environment. Moreover, there arises a problem that in rectangle substrates or disc-shaped substrates having a large diameter of 12 inches or more, turbulent air is generated at the circumferential portion of the substrates so that the film thickness uniformity of this portion becomes deteriorated.
As a method of applying a liquid uniformly onto the whole of a substrate without vain use of the liquid, Jpn. Pat. Appln. KOKAI Publication No. 2-220428 describes a method of dropping a resist from many nozzles which are arranged along one line and, spraying from the back thereof, a gas or a liquid onto a film-forming surface to obtain a uniform film. Jpn. Pat. Appln. KOKAI Publication No. 6-151295 describes a technique wherein many spray nozzles are made in a rod and a resist is dropped out from them onto a substrate in order to obtain a uniform film. Furthermore, Jpn. Pat. Appln. KOKAI Publication No. 7-321001 describes a method of using a spray head in which many spray nozzles for spraying a resist are made and moving the head relatively to a substrate to perform application.
In all of these applicators, plural dropping or spraying nozzles are arranged along one rank and they are scanned in order to obtain a uniform film. Besides application methods using a device having these nozzles, there is known a method of using a single liquid jetting-out nozzle and the nozzle is scanned over a substrate to be processed, so as to form a liquid film.
These methods have a problem that the processing time per substrate becomes long dependently on a method of handling the nozzle(s) or the use amount of a liquid gets very large.
An object of the present invention is to provide a liquid film forming method making it possible to shorten processing time and suppress the use amount of a liquid.
In order to attain the above-mentioned object, the present invention is as follows.
(a) A first aspect of the liquid film forming method according to the present invention is a liquid film forming method of dropping a liquid adjusted to be spread into a give amount on a substrate to be processed from a dropping nozzle or dropping nozzles of a dropping unit onto the substrate, and then moving the dropping unit and the substrate relatively while keeping the liquid dropping on the substrate, so as to form a liquid film on the substrate,
wherein the relative movement of the dropping unit and the substrate is composed of straight movement along a file direction in which the dropping unit passes from one end side of the substrate through an upper space of the substrate to the other end side of the substrate, and movement along a rank direction outside the substrate,
movement length along the file direction is the sum of dropping length (L) over the substrate and length of an acceleration/deceleration section, and
movement speed (v) along the file direction over the substrate is defined dependently on the square root of the product of the dropping length (L) and the absolute value of acceleration/deceleration (a) within the acceleration/deceleration section.
(b) A second aspect of the liquid film forming method according to the present invention is a liquid film forming method of dropping a liquid adjusted to be spread into a give amount on a disc-shaped substrate which is to be processed and has a diameter (D) has from a dropping nozzle or dropping nozzles of a dropping unit above the substrate, and then moving the dropping unit and the substrate relatively while keeping the liquid dropping on the substrate, so as to form a liquid film on the substrate,
wherein the relative movement of the dropping unit and the substrate is composed of straight movement along a file direction in which the dropping unit passes from one end side of the substrate through an upper space of the substrate to the other end side of the substrate, and movement along a rank direction outside the substrate, and
movement speed (v) along the file direction is defined dependently on the square root of the product of constant 0.4, the diameter (D) of the substrate, and the absolute value of acceleration/deceleration (a) before and after the time when the movement speed (v) is given.
Preferred embodiments of the above-mentioned inventions are as follows.
Dropping amount (W) from the dropping nozzle or the dropping nozzles of the dropping unit positioned over the substrate is defined dependently on an amount proportional to the movement speed (v).
The dropping unit has plural dropping nozzles and the dropping amount (W) is the total amount of the liquid dropped from all of the dropping nozzles.
The liquid is any one selected from an antireflection material, a resist material, a low dielectric material, an insulating material, a wiring material and a metal paste.
The liquid film is formed, using the liquid having a characteristic that when a minute amount of the liquid is dropped onto a minute area of the substrate, a change amount of a contact angle of the liquid to the substrate is within xc2x12 degrees during a time from 5 seconds to 60 seconds after the dropping of the liquid.
(c) A third aspect of the liquid film forming method according to the present invention is a liquid film forming method of dropping a liquid adjusted to be spread into a give amount on a substrate to be processed from a dropping nozzle or dropping nozzles of a dropping unit onto the substrate, and then moving the dropping unit and the substrate relatively while keeping the dropped liquid on the substrate, so as to form a liquid film on the substrate,
wherein the relative movement of the dropping unit and the substrate is composed of straight movement along a file direction in which the dropping unit passes from one end side of the substrate through an upper space of the substrate to the other end side of the substrate, and movement along a rank direction outside the substrate, or is composed of spiral movement in which the dropping unit goes from the substantial center of the substrate to the periphery thereof or from the periphery of the substrate to the substantial center thereof, and
a change amount of a contact angle of the liquid to the substrate is within xc2x12 degrees during a time from 5 seconds to 60 seconds after the dropping of the liquid when a minute amount of the liquid is dropped onto a minute area of the substrate.
A preferred embodiment of the above-mentioned invention is as follows.
Control of the change amount of the contact angle of the liquid dropped onto the substrate to the substrate within xc2x12 degrees is attained by adjusting the ratio of a surfactant to a solvent and an application agent constituting the liquid.
(d) The liquid for application according to the present invention is a liquid for application used in a liquid film forming method of dropping the liquid adjusted to be spread into a give amount on a substrate to be processed from a dropping nozzle or dropping nozzles of a dropping unit onto the substrate, and then moving the dropping unit and the substrate relatively while keeping the dropped liquid on the substrate, so as to form a liquid film on the substrate,
comprising a solvent, an application agent, and a surfactant,
wherein the ratio of the surfactant to the solvent and the application agent is adjusted in such a manner that when a minute amount of the liquid is dropped onto a minute area of the substrate, a change amount of a contact angle of the liquid to the substrate is within xc2x12 degrees during a time from 5 seconds to 60 seconds after the dropping of the liquid.
(e) A fourth aspect of the liquid film forming method according to the present invention is a liquid film forming method of dropping a liquid adjusted to be spread into a give amount on a substrate to be processed from a dropping nozzle or dropping nozzles of a dropping unit onto the substrate, and then moving the dropping unit and the substrate relatively while keeping the liquid dropping on the substrate, so as to form a liquid film on the substrate,
wherein the relative movement of the dropping unit and the substrate is composed of straight movement along a file direction in which the dropping unit passes from one end side of the substrate through an upper space of the substrate to the other end side of the substrate, and movement along a rank direction outside the substrate, or is composed of spiral movement in which the dropping unit goes from the substantial center of the substrate to the periphery thereof or from the periphery of the substrate to the substantial center thereof, and
a dropping area is defined in such a manner that when the liquid film is spread by its fluidity, the liquid does not extend over a boundary step of the substrate film in the edge area of the substrate.
(f) A fifth aspect of the liquid film forming method according to the present invention is a liquid film forming method of dropping a liquid adjusted to be spread into a give amount on a substrate to be processed from a dropping nozzle or dropping nozzles of a dropping unit onto the substrate, and then moving the dropping unit and the substrate relatively while keeping the liquid dropping on the substrate, so as to form a liquid film on the substrate,
wherein the relative movement of the dropping unit and the substrate is composed of straight movement along a file direction in which the dropping unit passes from one end side of the substrate through an upper space of the substrate to the other end side of the substrate, and movement along a rank direction outside the substrate, or is composed of spiral movement in which the dropping unit goes from the substantial center of the substrate to the periphery thereof or from the periphery of the substrate to the substantial center thereof, and
relationship between the distance from a dropping start position along the rank direction to a boundary step of the edge of the substrate and that from a dropping finish position along the rank direction to the boundary step of the edge thereof is set so that the former distance is large and the latter distance is small, and the distance between an end of the liquid film and the boundary step of the edge along the file direction is set so as to gradually become smaller from the dropping start position to the dropping finish position.
The present invention has the above-mentioned features so as to have the following effects and advantages.
By deciding the movement speed along the file direction under the above-mentioned conditions, it is possible to shorten the time for forming the liquid film on the substrate and suppress the use amount of the liquid.
Moreover, by deciding the dropping amount (W) from the dropping unit dependently on an amount proportional to the movement speed (v) or making the dropping amount constant, it is possible to make the thickness of the liquid film formed on the substrate uniform.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.